Voltage source inverter is a necessary circuit for driving a motor. By controlling the status of open or close of the components in the voltage source inverter, it can generate required current to drive the motor. Traditional control strategies of three-phase voltage source inverters include sinewave pulse-width modulator, SPWM, and space vector pulse-width modulator, SVPWM. Multiple-phase motors are advantageous over three-phase motors in the improvement of magnetomotive forces, the reduction of stator copper losses, the increase of motor operation efficiency, the noise reduction and the reduction of pulsating torque. When considering driving a multi-phase motor, one would face the issue of expansion for using either one of the two traditional types of modulators.
However, the strategy of controlling the multi-phase voltage source inverter and the applicability thereof are important when considering taking advantage of the multiple-phase motors. Although the operation of a SPWM is quite simple, and is easy to be expanded to multi-phase structures, the DC voltage usage rate thereof is decreased along with the increase of the number of phases, which is thus impractical. The use of several types of multi-phase SVPWM is restricted due to the required massive calculation circuit for performing calculations of high dimensional matrix inverse and trigonometric functions as well.